New Zealanders in Thailand say it appears to be life as usual despite the military seizing control of the country.

Thailand's military declared martial law before dawn (local time) today after anti-government protesters in Bangkok said they were moving to replace the country's crippled government.

Troops were moving throughout Bangkok after the announcement by army chief Prayuth Chan-ocha.

The Ministry of Foreign Affairs and Trade said 990 New Zealanders were registered in Thailand.

There could be many more who were not registered, but the ministry said no requests for consular assistance or advice had been made.

Troops seized the country's main television broadcaster before 6am Bangkok time (11am NZ time)

A ticker message on Channel Five read: "Army is to ensure the safety of all sides ... no need to worry."

Other troops massed at key parts of the city.

The ministry advised there was "high risk" in southern provinces and border regions and "some risk" to Kiwis' security elsewhere in Thailand.

New Zealanders were advised to avoid demonstrations and large public gatherings, it said.

It recommended monitoring events through the local media and adhering to any instructions issued by authorities.Jarrod Rayner, a New Zealander teaching at an international school in the heart of Bangkok, said life was going on as normal.

"The faces and actions of our student body would not suggest anything is happening. This is a big city, change happens, turmoil is a usual slice of life, politics is always uneasy."

He was feeling so at ease that he said he was about to take his 3-year-old to the park to play.

Taryn Wilson, a Kiwi journalist living in Bangkok, said so far this morning the situation had been calm and people were going about their business.

"I personally don't feel unsafe at the moment.

"Anti-government protesters have been on the streets - camping, marching and barricading major roads in the city - since November last year and they have been targets of grenades and gunfire. The army has also been set up bunker stations all around town for months.

"We have all learned how to monitor things, move around the city to avoid hot spots, and go about our business as best we can."

Today's events had upped the ante and people were waiting to see how it played out during the course of the day and over the coming days, she said.

Prayuth said on television that martial law had been imposed at 3am Bangkok time.

People's movement was allowed and no curfew had been imposed, he said.

The number of tourists visiting the country has dropped sharply since protesters took to the streets last November in a campaign to topple the government.

Prayuth asked all groups to stop political activities and enter a period where problems could be solved.

The army had set up a peacekeeping command, replacing the government's Centre for the Administration of Peace and Order, he said.

He was in charge of the command centre, which had the authority to summon people to be interrogated or to hand over documents and evidence to authorities, he said.

Prayuth ordered all government agencies except the army, navy and air force to return to their normal duties.

The armed services had authority to support operations of the command centre, he said.

The government was not consulted about martial law but remained in place, a government aide said.

"This martial law is just to restore peace and stability," deputy army spokesman Colonel Winthai Suvari said.

"It has nothing to do with the government. The government is still functioning as normal.''

Troops were seen at Bangkok's Victory Monument, where anti-government protesters have been rallying for months.

The army's move came after a meeting between the government and the Senate yesterday failed to break the impasse.

Prime Minister Niwattumrong Boonsongfpaisan refused to step down to pave the way for an interim government as demanded by establishment-appointed senators and anti-government protesters.

Observers described the meeting as "unsatisfactory".

The government has been preparing for an emergency response to threatened strikes by unions this week.

Key unions have swung their support behind the anti-government movement.

The air force said it was ready to provide public services if they were disrupted by strike action.

The government, however, is likely to welcome the military's intervention as long as it stops short of a coup.

Ministers insist that new elections are the only way to break a political impasse.

But anti-government protesters have been demanding the resignation of the government and the appointment of an interim prime minister and administration to run the country for up to two years during a reform period.

They disrupted elections in February and have vowed to do the same if new elections were held.

The Bangkok Post's military writer wrote on Twitter: "Everything now [is] on General Prayuth's shoulders."

Tensions soared in Bangkok last week as former prime minister Yingkluck Shinawatra was forced from office by a controversial ruling of Constitutional Court judges.

Her supporters saw the ruling as being part of a campaign by influential figures in Bangkok's royalist establishment to force her wealthy family to quit politics.

Prayuth has resisted calls by protesters to intervene in Thailand's six months of crisis that has left 29 people dead, hundreds injured and hit Thailand's economy.